Common Choke Cherry
Prunus virginiana
Choke Cherry may be a shrub or grow to 21 feet, and it always appears stiff. It has many short, leafy side branches and spikes of little white five-petaled flowers near the branch tips.  The fruit is a small dark red and deep purple when ripe drupe and makes a good jelly with apple juice.
Black Choke Cherry
Prunus meganocarpa
This is a Rocky Mountain variety that has more flowers, no glands at the base of the leaf blade, and the tasty drupe is almost black when ripe.
Southwest Choke Cherry
Prunus virens
This taller variety has somewhat pointed, glossy, black drupes.